Actually, I like bowling against lefties, they don't use my track. Not even the righties use my track because I play so deep. I normally only use one ball, sometimes two if #1 ball looses steam, and depending on how quickly the lanes break down, I may resort to a ball with a bit more power to finish.
But as far as bowling lefties, to me it doesn't matter who it is, in my mind, I can take them.